While various techniques have been explored for detecting seeds falling in a tube, the most commonly used technique is that of a light source and photo sensor which detect the passage of seeds by counting pulses generated by the momentary reduction in light intensity from the steady state intensity caused by the passage of a seed between the light source and the sensor.
The vast majority of products of this type actually manufactured and sold in the marketplace have been manufactured by Dickey-John Corporation and they have obtained issue of a number of patents in this field. In particular the following patents of Dickey-John have some relevance in this field.
U.S. Pat. No. 3,723,989 (Fathauer) discloses an arrangement in which the intensity of the light source is varied to accommodate changes in reception by the sensor due to dirt or dust collecting between the light source and the sensor.
U.S. Pat. No. 4,555,624 (Steffen) discloses a technique for analyzing the pulses generated by the momentary change in intensity value by following the changes in direction in the pulse and by generating individual positive and negative square-wave pulses in response to each change in direction.
U.S. Pat. No. 4,307,390 (Steffen) discloses an arrangement including a plurality of light sensitive sensors and an arrangement in which the number of counts or pulses recorded is increased relative to the number of input signals in dependence upon which one or ones of the plurality of light sensitive sensors are activated and in dependence upon the rate at which the signals are produced.
U.S. Pat. No. 4,166,948 (Steffen) discloses an arrangement in which the amplitude of the pulses is maintained above a predetermined minimum value by the sensor circuit, despite reductions in light intensity due to the accumulation of dirt and dust.
U.S. Pat. No. 4,635,215 (Friend assigned to Deere & Company and issued Jan. 6, 1987) provides a yet further technique which has not achieved any commercial success. U.S. Pat. No. 4,634,855 of the same inventor is filed on the same date issued on the same date and includes exactly the same disclosure. These patents utilize a technique in which the signal is amplified by an operational amplifier and then is analyzed using an analog to digital technique in which the area under each pulse is detected by integrating the sequential digital signals. This area is then compared with the area generated by other pulses to determine those which are representative of more than one seed.
As set out in the above patents, one problem which arises in relation to seed counters of this type is that it is necessary to include in the count those seeds which pass the sensor simultaneously or partly overlapping or otherwise simply counting a number of pulses would significantly undercount the number of seeds actually passing. This correction factor varies in dependence upon the type of seeds involved in the counting including the size of the seeds, the rate of passage of the seeds, and the geometrical shape of the seeds, since some seed shapes tend to produce a dipped pulse similar to an appearance to overlapping pulses from two seeds.
A further problem relates to the accumulation of dust and dirt which can vary the intensity of light normally received by the sensor.
A yet further problem relates to the geometry of the light source and the sensor which can either leave areas of the duct which are not properly monitored or can generate spurious reflections thus distorting the pulses. This invention relates to a method for communication between components of a machine which can be used for monitoring operation of a machine and/or for actuating or controlling various aspects of the machine. The invention is particularly but not exclusively designed for use with agricultural machines such as seeders, planters and the like.
Devices for monitoring seeders, planters and the like have previously been proposed, and generally these include sensors or transducers at various locations on the device for detecting various parameters of the operation of the machine. Thus one well known requirement for a sensor is that of detecting seed flow or seed movement. In an air seeder it is often desirable to detect the flow of seeds in an air tube to provide an indication of the rate of flow which can be also used to detect a blockage or zero flow. Further sensors have been provided for detecting the rate of rotation of shafts of the machine either for detecting seed supply rate or for detecting other parameters such as ground speed as detected by rotation of an axle. Yet further sensors have been provided for detecting a level of filling of a supply tank.
Generally the detection apparatus includes a central control unit with a key pad for allowing manual data entry, a display for providing information to the operator and a communication system for communication between the central control unit and the individual sensors. Generally devices of this type have used sensors which are simply switches or transducers which therefore provide a simple detection of a parameter to be detected and transmit a signal to the central control unit on detection of the parameter. Thus the conventional sensor does not include any memory or logic control so that the information is not acted upon or stored at the sensor itself. Such sensors require direct communication from the sensor itself to the control unit thus requiring individual wiring from each sensor to the control unit.
As the monitoring devices of this type become more complex and require more parameters to be monitored, the complexity of such individual wiring arrangements significantly increases cost and installation complication.
In addition to the monitoring function the present invention can also be used in relation to combined monitoring and control functions and also in relation to communication protocols between elements of a control system which does not include any monitoring function.